I disagree. I have two girls. One is an absolute angel in public, and at home. Never made a peep, not even as a newborn. The other was an absolute terror, in public and at home. I rarely took her anywhere until she was about three years old, because I did not want to disturb everyone around us.
However, I guess I am not that ill-mannered, because I had enough sense to leave her home with a sitter or her father until she could behave in public.
I certainly will say there are exceptions to every rule, and there are kids that are just bad without the parents' doings, but the general rule is that bad parenting gives rise to bad kids, and therefore, the parents' fault.